Paramyxovirus implicated in SARS as cases reach 264

Mar 19, 2003 (CIDRAP News) – As cases in the global outbreak of "severe acute respiratory syndrome" (SARS) climbed to 264 today, the World Health Organization (WHO) said there is evidence that the illness may be caused by a previously unknown member of the Paramyxovirus family, which causes measles, mumps, and canine distemper.

Researchers at laboratories in Germany and Hong Kong detected particles of a virus from the Paramyxoviridae family in samples from SARS patients, WHO officials said in a news release. "This is the first major step forward in efforts to pinpoint the causative agent," the statement said. "The failure of all previous efforts to detect the presence of bacteria and viruses known to cause respiratory disease strongly suggests that the causative agent may be a novel pathogen."

The SARS outbreak has caused 9 deaths among 264 suspected or probable cases in 11 countries, including 11 suspected cases in the United States, according to WHO. Most of the cases are in Southeast Asia, with 150 in Hong Kong alone, but some are reported in Canada, Germany, the United Kingdom, Slovenia, and Spain. The illness has caused 5 deaths in Hong Kong, 2 in Canada, and 2 in Vietnam. Many of the patients are healthcare workers who treated other SARS patients.

The WHO case count does not include 305 cases of atypical pneumonia, with five deaths, that occurred in the Guangdong province of China, near Hong Kong, in recent months. It remains unclear whether those cases were SARS, Julie Gerberding, MD, director of the Centers for Disease Control and Prevention (CDC), said today.

The SARS outbreak, under investigation by WHO since mid-February, last week prompted the WHO to issue its first global outbreak alert in 10 years. WHO has described the syndrome as an influenza-like illness that begins with a fever, muscle aches, headache, and sore throat and may progress to pneumonia and acute respiratory distress. No specific treatment for the condition has yet been identified.

The WHO statement said the Paramyxovirus family includes many well-known viruses associated with respiratory infections, including respiratory syncytial virus, mumps, and measles. Some of these are widespread, especially in winter. Therefore, "It cannot be ruled out entirely that tests for the SARS agent are detecting such 'background' viruses rather than the true causative agent," the statement said.

WHO officials said research by an international network of 11 leading research laboratories is expected to lead to the definitive identification of the SARS agent. The lab network was set up Mar 17. The agency hopes that identification of the pathogen will lead to a specific drug treatment and speed the development of a diagnostic test.

At a CDC news conference today, Gerberding called the evidence from more than one lab that the pathogen may be a paramyxovirus "an encouraging step forward." She added, "But seeing something in a nasal swab isn't the same thing as identifying it as the cause. A great deal more works needs to be done."

The 11 US patients with suspected cases have fever, respiratory symptoms, and a history of recent travel to areas involved in the outbreak, Gerberding reported. "The symptoms of concern are fever, cough, and difficulty breathing or chest discomfort, and during flu season these are extremely common symptoms," she said. "So the travel history is extremely important here. We don't want people who haven't traveled to these regions to be concerned about this problem at this particular time."

The CDC is working to advise travelers that they should seek medical attention if they get a fever or other SARS symptoms within 7 days of returning from Hong Kong or other affected areas, Gerberding said. The agency activated its emergency operations center Mar 14 after learning of cases in Canada among travelers recently returned from Southeast Asia.

Gerberding said most cases so far are in household contacts of SARS patients and healthcare workers who have had direct contact with patients. Transmission is probably by droplets, but airborne transmission has not been ruled out, she said. The CDC's current infection control guidelines for SARS call for standard precautions, airborne precautions (a negative-pressure room, use of N-95 respirators), and contact precautions (gown and gloves).

"One of the good pieces of news we've been receiving from WHO is that there does seem to be success in containing SARS in the healthcare environment when these precautions are implemented," Gerberding said. She also said the CDC has learned that several patients in Hanoi and Hong Kong seem to be improving.

In another development, the Hong Kong Department of Health reported that seven people who contracted atypical pneumonia (SARS) recently had stayed on the same floor of a hotel in Kowloon, a city on the Chinese mainland that is part of Hong Kong. The seven people stayed at the hotel between Feb 12 and Mar 2 and they experienced pneumonia symptoms between Feb 15 and 27, the department reported in a news release.

Because it's not clear just how contagious the illness is, Gerberding said investigators want to determine how much contact the hotel visitors had with each other. "We know that two of them were close visitors with each other; we don’t know how often they visited," she said.